The present invention is directed to an attachment device including a cover plate and a fastening element for securing a structural component to a solid foundation unit where the structural component has an opening with a non-circular cross section. The opening is formed of a round bore and two symmetrically arranged widening sections located diametrically opposite one another on opposite sides of the bore. The width of the widening sections measured parallel to the axis of symmetry of the sections increases in the direction outwardly from the round bore. The cover plate at least partially covers the opening and includes a round through passage and projections located diametrically opposite one another and engageable into the widening sections of the opening through the structural component, with the projections each located on a planar surface and on opposite sides of the through passage.
For securing structural components to shaped rails, devices are used, such as disclosed in DE-OS 42 43 185, made up of a fastening element, a rail nut with a non-circular head and a cover plate extending over and at least partially covering a non-circular opening in the component and with projections extending into the opening. To assure a simple and rapid preliminary assembly of the device to other components, the non-circular head of the rail nut is matched to the cross section of the opening in the structural component, so that the rail nut of a threaded connection can be passed in a specific angular position through the opening in the structural component without the necessity of unscrewing the rail nut from the attachment element.
To secure the structural components to a solid foundation unit, the cover plate of a known device can be used so that a fastening element in the shape of a screw or bolt can be guided centrally in the opening. In the cooperation of the attachment element with a dowel element disposed in the foundation unit, a contact pressure force can be developed by the fastening element acting on the structural component through the cover plate. Since the known cover plate protrudes only on two sides beyond the non-circular opening and thus rests only on the component in two regions lying diametrically opposite one another, such a high specific area pressure can develop causing a deformation of the opening in the form of a narrowing down. Further, use of such component along with threaded connections is no longer possible, since the rail nut of the threaded connection cannot pass through the opening.